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Orange County Health Department Improvements Smith Sinnett /2024008 Hillsborough,NC Orange County Asset Management Services HVAC DUCTS AND CASINGS 23 31 00 - 6 or other architectural details before fabricating or installing duct. Consult Designer where conflicts arise between ductwork and other utilities which cannot be resolved by relocating duct. F Where offsets in ductwork are required,contractor to use standard 30,45 or 90-degree elbows. Where space constraints do not allow for the use of standard elbows for offsets,use of angled offsets as depicted by SMACNA Figure 2-7 (Angled Offset Type 1)may be used with maximum angle of offset not to exceed 15 degrees maximum.Offsets Type 2 and 3 in SMACNA Figure 2-7 shall not be allowed. G Rectangular Duct Elbows: 1.Rectangular Duct:Unless specific type is indicated,provide radius elbows with splitter vanes with minimum centerline radius to width or diameter ratio of 1.5 a.1.5 radius elbows with full splitter vanes as follows: 1)One vane for duct width 2-12" 2)Two vanes for duct width 13-20" 3)Three vanes for duct width 21"-36" 4)Four vanes for duct width 38"and larger 5)Fabricate vanes in accordance with SMACNA. b.Rectangular throat elbows with turning vanes where 1.5 radius elbows do not fit. c.Rectangular throat/radius heel elbows or rectangular elbows without turning vanes shall not be used. H Round and Oval Duct Elbows: 1.Unless specific type is indicated,use radius elbows with centerline radius to diameter ratio of 1.5. ONLY where1.5 radius elbows do not fit,1.0 radius elbows may be used if approved by the Engineer. I Construct ductwork so that interior surfaces are smooth. Internal duct hangers and internal bracing are not allowed. Refer to above for internal tie rods. J Support coils,filters,air terminals,dampers,sound attenuating devices,or other devices installed in duct systems with angles or channels and make all connections to such equipment including equipment furnished by others. Secure frames with gaskets,nuts,bolts and washers. K Flexible ducts shall not exceed 5 feet in length.Bends,kinks,and sagging of flexible duct will not be accepted.The maximum permitted sag is 1/2"per foot of support spacing. L Install outside air intake duct to pitch down at minimum 1”per 20 ft toward intake louver or plenum and to drain to outside of building. Solder or seal seams to form watertight joints. M Install exhaust air duct to pitch down at minimum 1”per 20 ft toward exhaust louver. N Where 2 different metal ducts meet,install joint in such a manner that metal ducts do not contact each other by using proper gasket seal or compound. O Flexible Ducts: Connect to metal ducts with adhesive plus sheet metal screws. 1.Flexible ducts are not allowed for special exhaust systems,such as laboratory exhaust,vehicle exhaust, etc. 2.Splicing of flexible duct will not be allowed. 3.Flexible ducts shall not pass through any partition,wall,floor,or ceiling. P Duct sizes indicated are precise inside dimensions.For lined ducts,maintain sizes inside lining. Q Provide openings in ductwork as indicated to accommodate thermometers and controllers.Provide pilot tube openings as indicated for testing of systems,complete with metal can with spring device or screw to insure against air leakage.For openings,insulate ductwork and install insulation material inside a metal ring. R Locate ducts with sufficient space around equipment to allow normal operating and maintenance activities. S All exposed ductwork to be painted shall be mill bonderized or "paint grip."The contractor shall thoroughly clean all ductwork surfaces to be free from oils,grease,lubricants,and other contaminants prior to application of paint.Follow T Paint interior of metal ducts that are visible through registers and grilles and that do not have duct liner. Apply one coat of flat,black,latex paint over a compatible galvanized steel primer. U Use double nuts and lock washers on threaded rod supports. Docusign Envelope ID: 2D852F9B-A7CF-462A-9536-444A53AA848A